Windshield-washing systems for motor vehicles are known in which the wiper blade is moved essentially back and forth parallel to itself (at a an unchanging orientation) over the windshield to be cleaned. In such windshield-washing systems a wiper arm and a guide arm oriented parallel to it are used to form a parallelogram by means of a coupling element, with the wiper blade being suspended on this coupling element. Typically two, spaced apart, bearing bolts are provided on this coupling element, housed in a bearing bushing at the end of the wiper arm or the guide arm, respectively.
In a wiper system of this type known from DE-OS 39 17483, in which the driven wiper arm and the guide arm are constructed identically and have, in each case, a fastening part, a joint part and a wiper rod fastened to this joint part and made of flat strip steel of defined width and thickness, the free end of the wiper rod is broadened by a stamping process. After the stamping process, a housing opening is made in the broadened section of the wiper rod by punching, and finally a bearing bushing with or without an internal bushing is inserted by wobble-riveting or rolling.
Although such a wiper arm can be economical, particularly by combining different machining steps, such as cutting the wiper arm to length from flat strip steel and simultaneous stamping of the broadened arm of the wiper rod, several problems have resulted. Due to cold-forming, the material of the wiper rod becomes much stronger in the broadened area, so that the service lives of the tools for punching the housing opening are relatively short, which in turn leads to a cost increase. Also the insertion of the bearing bushing in the housing opening is complicated.
The present invention overcomes these problems by providing an improved wiper arm which can be produced economically without its functionality suffering.
The invention is based essentially on the consideration that the bearing bushing oriented across the width of the wiper rod is a component of a bearing device produced as a plastic part, with the bearing bushing having an elongated, laterally projecting fastening sleeve with which the bearing device is press-fit onto the free end of the wiper rod and locked in place. Such products can be produced extremely cheaply today as mass-production items, with injection molding being particularly suited of an overall single-piece production of such a plastic part.
The wiper rod itself is likewise very simple to produce. The wiper rod material need only be cut to length from the flat strip steel supplied in meter lengths or as a roll. If an appropriately designed cutting/stamping tool is used, a catch means for the fastening sleeve of the bearing device can be produced on the free end of the wiper rod during the separation process.
The assembly process of the bearing device at the free end of the wiper rod is advantageously simple in a single work step. Moreover, there is the possibility, if desired, of removing the entire bearing device without great effort and replacing it with a new one.
In order to permit a simple and uncomplicated engagement of the bearing device with the attachment sleeve on the free end of the wiper rod, it is recommended that at least one catch element, especially in the form of a catch spring or a flexible tongue, be provided on the attachment sleeve; when pushing the engagement sleeve onto the wiper rod end, it automatically moves into engagement with a corresponding catch element, preferably a pressed-out catch lug on the wiper rod end.
In order to guarantee a proper guidance of the wiper blade, the bearing device should be fastened tightly and as free of play as possible to the wiper rod. Hence, according to an advantageous design, inward-projecting profiles are provided on the inside of the attachment sleeve with a free cross section corresponding essentially to the cross section of the wiper rod, particularly to compensate for tolerances.
If, according to another design of the solution according to the invention, the bearing bushing is constructed in a pot shape, the closed end of the bearing bushing is protected from the ingress of dirt and moisture without the need for any special measures for this purpose. Unlike wiper arms of the prior art, protection is thus guaranteed without having to machine an extra circumferential groove in the outer side of the bearing bushing in which a special plastic cap must then be clipped in.
The bearing bushing of the bearing device fastened to the wiper rod is intended to house an articulation pin, with an axial positional retention of the articulation pin with respect to the bearing bushing, or conversely of the bearing bushing with respect to the articulation pin, required for the secure functioning of the bearing. In contrast to the solution cited as prior art, in which a lock washer arranged in an annular groove of the articulation pin provides an axial position retention, the bearing device is to be locked into place on the articulation pin or on the component supporting the articulation pin, according to one design of the solution according to the invention. To this end the bearing device has corresponding catch elements, which can be brought into engagement with corresponding catch elements on the articulation pin or on the respective component.
Such catch elements can advantageously be segments of an annular lip which are directed radially inwards on the inside of the bearing bushing and can be brought into engagement with a corresponding annular recess in the outer surface of the articulation pin.
Thus, an axially-retained catch connection between bearing bushing and articulation pin can be produced which guarantees the required ability of the articulation pin to be twisted inside the bearing bushing.
According to another advantageous design, the radial yielding of the segments of the annular lip should be guaranteed during the installation of the bearing bushing on the articulation pin, in order to make it easier for the bearing bushing to snap into place on the articulation pin and thus avoid damage, especially to the annular segments. For this purpose, the bearing bushing has segment-shaped relief cuts in the vicinity of the segments of the annular lip and extending from the open end of the pot-shaped bearing busing up to it closed. The segments of the annular lip that act as catch elements are thus located on the inside of wall segments of a hollow cylinder and, upon insertion of the articulation pin, the wall segments are capable of elastic radially outward yielding due to the presence of the relief cuts. This also makes possible a nondestructive disassembly of the bearing connection with sufficiently cautious application of force in the axial direction of the bearing bushing or the articulation pin.
In case a pot-shaped bearing bushing is used, one end of the bearing bushing is already protected from the infiltration of dirt or water which might be detrimental to the smooth running of the friction bearing. In order to ensure such protection for the friction bearing on the open end of the bearing bushing as well, the bearing bushing has an expanded cylindrical opening at its open end. On the wall of this expanded cylindrical opening, an annular sealing lip is provided, preferably molded in one piece onto the inside of this opening. This sealing lip could, of course, also be replaced by a sealing ring inserted into an annular groove. Upon engagement of the bearing bushing on the articulation pin, the sealing lip comes into sealing contact with an expanded cylindrical base component of the articulation pin.
In order that, on the one hand, a sufficient seal is guaranteed, but, on the other hand, an excessive radial contact pressure of the sealing lip does not lead to sluggishness of the friction bearing, it is advantageous if the bearing bushing has a continuous annular groove, axially open and arranged coaxially to the expanded cylindrical opening. This annular groove, which acts as a relief cut, permits an elastic radial yielding of the annular sealing lip. The sealing lip is thus located in a certain sense on the inside of a hollow cylindrical wall that is elastically expandable to a certain extent.
The invention will be described in greater detail below on the basis of an embodiment.